Numerical control system

A system for controlling the position of a movable member relative to a stationary member, said system comprising:

• a reversible motor means for moving said movable member along a predetermined path of movement;
• a position transducer operatively connected between said movable and stationary members, said transducer having a pair of inputs and an output;
• clock means for generating an output frequency at a highly elevated first frequency;
• a sinusoidal wave generator having an input directly connected to the clock means output, said wave generator being operable to produce a pair of sinusodial wave outputs at a predetermined second frequency, said second frequency being equal to said first frequency divided by a predetermined constant, said sinusoidal wave outputs having a predetermined and constant phase shift difference relative to each other and wherein each wave generator output is connected to one transducer input;
• said transducer being operable to vary the phase of its output signal in dependence upon the relative positions of said movable and stationary members;
• signal combiner means having two inputs and an output for adding the input signals together to form the output signal, said clock means output being connected to one of said combiner inputs;
• pulse generator means for generating an output train of pulses of a frequency and polarity corresponding to the desired speed and direction of movement of the movable member relative to the stationary member, said pulse generator means output being connected to the other input of the signal combiner, and said pulse generator means having two inputs, said clock means output being connected to one pulse generator means input for synchronizing said pulse generator means with said first frequency and a control circuit which generates a signal on an output indicative of the desired speed and direction of movement of the movable member, said control circuit output being connected to the other pulse generator means input;
• means for converting the frequency of the combiner means output to said second predetermined frequency by dividing said combiner means output by said predetermined constant;
• means for comparing the phase of the frequency converter means output and the transducer output and for generating an output signal representative of the phase difference;
• and
• means responsive to said phase comparing means for actuating said motor means.